Composite structures are employed in an increasing number of applications, such as a variety of automotive and aviation applications. Regardless of the particular application, composite components can be formed by laying up or stacking a number of plies, such as on a tool or mandrel which, at least partially, defines the shape of the resulting composite structure. The plies are thereafter consolidated, such as by an autoclave process, into an integral laminate structure.
In addition to conventional autoclave processes, composite components can be fabricated by a fiber placement process in which plies of fibrous tow pre-impregnated with thermoset or thermoplastic resin, typically termed prepregs, are individually placed on and consolidated to an underlying composite structure. Preferably, a laser heats the lower surface of the fiber-placed ply and the upper surface of the underlying composite structure to at least partially melt a localized region of the ply. Compactive pressure is then applied to the at least partially molten region of the ply, such as by a roller disposed downstream of the laser, so as to consolidate the fiber-placed ply and the underlying composite structure, thereby forming the integral laminate structure. One advantage of a fiber placement process is that the composite material can be cured on the fly, thereby reducing the time required to fabricate a composite part.
Another method of fabricating composite components is a resin transfer molding (RTM) process. According to a RTM process, a number of fibers, such as graphite or glass fibers, are woven to form a woven fiber intermediate structure. For example, the fibers can be woven on a loom-type structure as known to those skilled in the art. Resin can then be introduced to the woven fiber intermediate structure such that, once the resin has cured, the resulting composite component formed from the resin-impregnated woven fiber structure is created.
Regardless of the fabrication method, composite components oftentimes include a number of optical fibers which extend through the composite component in order to form communication paths, for example. In addition, composite components, such as composite components which form the external surface of an aircraft, ship, helicopter or submarine, typically include fiber optic sensors for monitoring the temperature or strain to which the structure is subjected. Although the types of composite components that include optical fibers are not limited to smart structures, smart structures that include electrical devices, such as in antennas, electroceramic actuators and integrated circuits, oftentimes also include a network of optical fibers for establishing communication between the various electrical devices and one or more processors or controllers which monitor or control the electrical devices.
In order to receive signals originating from outside the composite component and to transmit signals outside of the composite component, the optical fibers are commonly routed to and extend through the surface or edge of the composite structure. In this regard, a composite structure generally includes inner and outer surfaces through which the optical fibers extend. Most commonly, the optical fibers are routed through the inner surface of the composite structure. However, the surface egress of the optical fibers is primarily effective in instances in which a hollow composite structure is fabricated, such as a cylindrical object, i.e., a submarine hull or a missile body, which permits the fiber optics to be routed to the hollow interior of the composite structure. In contrast, in instances in which the composite structure is not hollow, such as a solid or a relatively planar composite structure, the surface egress of the optical fibers is less effective since the optical fibers will protrude from a surface, such as the exterior surface, of the composite structure and may interfere with the performance of the structure or be vulnerable to being sheared off.
Even in instances in which the composite structure is hollow, the optical fibers must typically be extended into the hollow mandrel or tool upon which the composite structure is formed. As such, the mandrel must define an opening through which the optical fibers will extend. After placing the innermost layers or plies upon the hollow mandrel, a corresponding opening must be formed or drilled through the innermost layers and in alignment with the opening defined by the mandrel such that the optical fibers can be inserted through the opening in the mandrel and into the hollow interior. As will be apparent, the process of forming the opening in the innermost layers can be quite tedious and time consuming in order to properly align the opening in the innermost layer with the opening in the mandrel.
The optical fibers are then inserted into the interior of the hollow mandrel in a random order. Consequently, the optical fibers can become entangled with each other or with other surface-egressed components, such as electrical leads, to form a tangled web which is relatively difficult to disentangle. In addition, the process of disentangling the optical fibers may inadvertently shear off one or more of the optical fibers.
In order to make the necessary optical connections with the optical fibers extending from a composite component, the optical fibers must first be disentangled. As will be apparent, the disentanglement of the optical fibers is a time consuming and tedious process. The optical fibers are also fragile and susceptible to being broken during the manufacturing process and, thus, must be handled in a delicate manner, thereby further complicating the disentanglement procedure. In addition, the optical fibers must be stored or located in a manner which does not impede the mechanical connection of the composite components or the performance of the resulting structure. Therefore, even though the optical fibers extending from a number of individual composite components can be interconnected, conventional techniques suffer from a number of deficiencies, including the time consuming and tedious nature of the interconnections, as described above.